A NEW SPECIES OF
CAVERNICOLOUS POTAMID CRAB
(CRISTACEA: DECAPODA: BRACHYURA: POTAMIDAE)
FROM SOUTHERN CHINASINOPOTAMONBAIYANENSE,ABSTRA CT. - One new species of potamid, Sinopotamon baiyanense, is described froma cave in Hunan Province, China. The new species is closely allied to Sinopotamon liuyanense
Dai, 1995, from Hunan Province, China and Sinopotamon nanlingense Dai & Jiang, 1991,
from Guangxi Province, China. The new species of Sinopotamon can be distinguished fromS. liuyangense and S. nanlingense by the form of the carapace, cheliped, male abdomen
and male first and second pleopods.

The freshwater crabs of China are very diverse and widely distributed. There are at least
some 160 species and subspecies of potamid crabs from southern and central part of Chinathat has been described (Ng & Dudgeon, 1992). The habitats of these crabs are also verydiverse. While most of them are found in ponds, open fields or mountain streams, there arevery few crabs found inside caves. Ng & Trontejl (1996) described Daipotamon minos
which was found inside a cave in Libo County, southeastern Guizhou, China. There are noreports on cavernicolous Sinopotamon in China to date. Recently, two specimens ofSinopotamon were collected from a cave in Hunan Province, China. Examination of thesespecimens showed that although they were similar to S. liuyangense Dai, 1995, and S.
nanlingense Dai & Jiang, 1991, there were enough morphological differences to recognisethem as new species, as proposed in the present contribution.
The specimens are deposited in the Institute of Zoology, Academia Sinica, (AS) and theZoological Reference Collection, School of Biological Sciences, National University ofSingapore (ZRC). The abbreviations Gland G2 are used for the male first and second

N. K. Ng - School of Biological Sciences, National University of Singapore, Kent Ridge 119260,
Republic of Singapore. Dai Ai- Yun - Institute of Zoology, Academia Sinica, 19, Zhongguancun Road,
Haidian, Beijing 100080, People's Republic of China.

pleopods (gonopods) respectively. The terminology adopted here follows Ng (1988). The
synonymy of Sinopotamidae Bott, 1970, under the Potamidae Ortmann, 1896, follows Ng(1988).

Sinopotamon baiyanense, new speciesi'·(Figs. 1, 2)

Materials examined. - Holotype, 1 male (AS, uncatalogued), carapace length 48.3 mm, carapace
width 37.1 mm; China: Northeastern Hunan Province, very near Hubei Province, Longshan County,Baiyan Cave (29.5°N, 109.4°E), colI. A. Bedos & L. Deharveng, 15 Aug.1995.
Paratype - 1 male (ZRC 1997.551), carapace length 49.5 mm, carapace width 39.7mm, same data
as holotype.

Description. - Carapace broader than long, not inflated, dorsal surface gently convex,
smooth, punctated especially on the anterior third; epibranchial region covered with finerugae and granules. Cervical groove broad, moderately deep, H-shaped groove between gastricand cardiac regions distinct. Cardio-intestinal region with shallow transverse groove;
pterygostomial, suborbital and sub-branchial regions smooth. Epigastric crest low, rugose;
postorbital crest low but distinct. Dorsal orbital margin ridged, ex-orbital angle triangular,outer margin with 6 granular teeth. Epibranchial tooth distinct, blunt, antero-Iateral margin
carinated with 13 serrated teeth and several granules. Frontal margin smooth, deflected,
enmarginated medially, supraorbital margin with fine, rounded grannules; infraorbital marginsmooth. Eyes developed.
Third maxilliped ischium rectangular, about 1.6 times as long as broad; merus mediallydepressed, about 1.2 times as broad as long, exopod reaching proximal 1/3 of merus, exopodwith well-developed flagellum, longer than width of merus.
Chelipeds unequal, outer surface gently rugose, fingers subequal to slightly longer thanpalm; carpus with a triangular spine on inner distal angle, small tooth at base; larger manus
about 1.4 times as long as high, about 1.1 times as long as movable finger, fingers close
without gap.
Ambulatory legs stout, second ambulatory leg longest, dactylus slender, cross-section
quadrate; surface of merus gently rugose, dorsal margin gently serrate to uneven, with small
blunt subdistal spine; last leg with propodus about 2 times as long as broad, slightly longer
than dactylus.
Surface of anterior thoracic sternites slightly punctate; median groove of thoracic sternum
moderately deep. Sutures between sternites 4/5, 5/6, 6/7 interrupted, space relatively broad;longitudinal suture between sternites 7 and 8 short.

Fig. 1. Sinopotamon baiyananse, new species, from Guizhou Province, southern China; holotype male.
A) carapace, B) third maxilliped, C) abdomen, D) natural position of the first pleopod, E, F, H) firstpleopod and its enlarged last segment, G) second pleopod.

broad as long, twice length of segment five; tel son tongue-shaped, about 1.2 times as broadas long, longer than segment six; lateral margins of telson deeply concave: lateral marginsof segment five and six gently concave: segment one rectangular, reaching bases of coxae
of fourth ambulatory leg.
G I stout, relatively straight, not reaching tuberacle of abdominal lock. Terminal segment
short, convex, bending gently inwards towards median part of thoracic sternum in situ (ventralview), tip slightly bifurcated with chitinous prominence, about 2.0 times as long as broad;subterminal segment about 5.2 times as long as terminal segment, distal part of outer margin
with distinct broad cleft; groove for G2 ventral in position; G2 subequal in length to G I,
distal segment well developed; basal segment about 3.1 times as long as distal segment.
Remarks. - The fr~shwater crabs of China are extremely diverse with more than 160species and subspecies reported from Guizhou Province (Dai et aI., 1984; 1985; Dai & Yuen,1988; Dai, 1990) and Wuling Mountain Area (Dai, 1995). The present two specimens proved
to be a new species of Sinopotamon very similar to S. liuyangense Dai, 1995, from Wuling
Mountain Area, a mountainous region between the borders of Hubei, Hunan, Guizhou andSichuan Provinces of China and S. nanlingense Dai & Jiang. 1991, from Guangxi Province,China.
Sinopotamon baiyanense can be differentiated from S. liuyangense by the following
characters viz: epibranchial region with fine rugae and granules (vs. rugose, without granules);cervical groove broad (vs. narrow); post-orbital crest relatively sharp (vs. blunt): front
distinctly deflected downwards (vs. slightly deflected): carpus of cheliped with a small toothat its base (vs. strong spine present); last leg with propodus about 2 times as long as broad(vs. 1.3 times); subterminal segment of the first male pleopod about 5.2 times as long asterminal segment (vs. 3.3 times in the latter); G I terminal segment convex (vs. nan-ow); andG2 basal segment about 3.1 times as long as last segment (vs. 2.3 times).

Fig. 2. Sinopotamon baimnense, paratype male. carapace length 48.3mlll and carapace width 37. I III III(ZRC 1997.551).

Sinopotamon baiyanense can be differentiated from S. nanlingense by the following
characters: G 1 penultimate segment about 5.2 times as long as last segment (vs. 3.2 times)
and the last G 1 segment is much more convex.
Ecology. - Baiyan Cave (White Rock Cave) is a small, relatively superficial cave (only10m under the plateau) with small streams. The average temperature is about 18.4 0C,
water temperature between 20.9 - 21.3 °C and pH is 8.7 - 8.8. The two specimens werecollected at about 150m from the entrance.
Sinopotamon baiyanense does not shows features typical of cavernocolous animals suchas reduced eyes, loss of body pigmentation or elongated pereiopods. The eyes are welldeveloped, filling almos'f the entire orbit but the cornea are not fully formed and not completelypigmented. It sebms likely that this species is predominantly cavernicolous but since thecave is relatively small and superficial, may make forays into the surrounding region. This
have been observed in cave species of freshwater crabs with well-developed eyes and body
pigmentation that nevertheless move into epigean habitats (Ng, 1989; 1992; Ng & Goh,1987; Ng & Trontelj, 1996).
Etymology. - This species is named after the type locality, Baiyan Cave in Longshan
County, Hunan Province, central China.

We would like to thank Dr. Louis Deharveng for the specimens and information on theBaiyan Cave; Dr. Peter Ng for subsequently passing the crab to us for study; Dr. Peter Ng,
Mr. Tan Swee Hee and the two referees for critically reading the manuscript; Mr. Yip Hoi
Kee for the photographs of the specimens.

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Received 14 Feb 1997
Accepted 15 May 1997